Conventionally, an obstacle around a vehicle is notified for a driver of the vehicle by using a display system. For example, a night vision system uses a far-infrared ray camera disposed on the vehicle to detect a position and/or a movement of a detecting object that emits an infrared ray, and recognizes that the obstacle is existing on a road ahead of the vehicle, or crossing a road. Further, the night vision system determines whether or not the object is a walker based on a size and shape of the object. Then, an image of a vehicle front field is displayed on a display unit for notifying the driver of the vehicle of the walker on an expected travel route of the vehicle or of the walker crossing the street.
However, the above system displays the image of the detecting object on the display unit that is disposed on an instrument panel or the like, thereby making it difficult for the driver to watch the display unit due to a requirement of a move of a look of the driver away from a windshield to the display unit.
Therefore, a display system that projects an image light to be reflected on the windshield to generate in a vehicle front space a virtual image in a view of the driver for information notification is proposed. For example, when a walker 101 that causes unsafeness of the subject vehicle is seen through a windshield 17 as shown in FIG. 7, the proposed system such as the one described on page 73 of a non-patent document of Automotive Technology 2006 Vol. 60 No. 2 can display a frame image 105 as a virtual image for surrounding the walker 101 for the purpose of notifying the driver of a position of the unsafe obstacle.
However, due to the vibration of the vehicle during driving, the frame image 105 is also vibrated, thereby making the positions of the images 105a, 105b, 105c at times T, T+1, T+2 respectively different from each other in the view of the driver as shown in FIG. 8. The respectively different position of the image 105 annoys the driver of the vehicle in a great deal.